ES2398716T3 - Collagen device and preparation procedure - Google Patents

Abstract

A collagen device for use as a substitute for the dura mater, said collagen device comprising: a sheet of crosslinked collagen, said sheet having a plurality of pores, most of said pores having a diameter of less than 10 microns .

Description

Collagen device and preparation procedure

Field of the Invention

The present invention relates to a collagen device. More specifically, the present invention relates to a collagen device for use as an implant to replace, strengthen or strengthen body tissue, an adhesion barrier, or for use as a short-term body contact for retention of the moisture, hemostasis or tissue protection.

Background of the invention

The human brain and spinal cord are covered with meningeal membranes whose integrity is critical to the functioning of the central nervous system. When the integrity of a person's meningeal membranes is intentionally or accidentally compromised, serious consequences can be derived from it, unless the membranes can be repaired.

The meningeal membrane comprises three superimposed layers of tissue, which are, in order from the outside in, the dura (or dura), arachnoid and pia mater. The repair of damaged meningeal membranes has mainly focused on implantable and / or absorbable constructs (known as dura substitutes) that are grafted onto the damaged dura and are designed to replace and / or regenerate damaged tissue.

Prior art in the field of the present invention includes US 5,997,895 A, which relates to the repair of damaged tissue, and more specifically, to the use of non-infectious collagen to cure damaged dural tissue. In addition, WO99 / 13902 A1 discloses hard substitutes, which include treated and / or prepared collagen to be physiologically compatible and which is substantially free of viruses and active prions. In addition, US 5 206 028 A discloses collagen membranes having physical and biological properties that make them suitable for medical uses, in particular as a periodontal barrier.

Summary of the invention

The present invention provides a collagen device for use as a dural substitute, said collagen device comprising: a crosslinked sheet, said sheet having a plurality of pores, the majority of said pores having a diameter of less than 10 micrometers. Surprisingly, the collagen device of the present invention has good handling properties, since the collagen device is flexible enough to adapt to irregularly shaped surfaces but is still rigid enough so that it does not bend or adhere to itself, to the practitioner's instruments or gloved hands when they are wet. In addition, the collagen device according to the present invention has very good resistance properties, such as tensile strength, which makes it very easy to be handled by the doctor. In addition, the collagen device according to the present invention may have the same shape or size as conventional collagen devices, such as the currently available hard collagen grafts, while still providing the surgeon with a device that has a resistance and superior handling properties.

The collagen device according to the present invention is substantially completely absorbable, although most of its pores have a diameter of less than 10 micrometers. Surprisingly, the present inventors have found that despite the fact that those skilled in the art believe that the pore size should be sufficiently large (a pore diameter of 150 µm is preferred for the internal pores and 70! m for the surface pores) to allow the growth of meningeal tissues to infiltrate it, the collagen of the present invention is replaced by growing meningeal tissue and is substantially absorbable even though a majority of its pores have a diameter of less than 10 μm.

The collagen device of the present invention can be prepared by mixing collagen with purified water for a period of time sufficient to form a mixture. The pH of the mixture is adjusted to a pH level sufficient to substantially solubilize the collagen. A first predetermined amount of the mixture is placed in a container. The mixture is subjected to a lyophilization process and formed into a collagen device. The collagen device is also crosslinked. The collagen device has a plurality of pores in which a majority of the pores have a diameter of less than 10 μm. To use the collagen device as an implant to replace, strengthen or strengthen the body tissue, or to act as an adhesion barrier, the collagen device contacts the body tissue and that contact is maintained until the collagen device It is substantially reabsorbed into body tissue.

Brief description of the drawings

The invention can be more fully understood from the detailed description that follows taken in conjunction with the accompanying drawings, in which:

Figure 1 is a flow chart illustrating a method of preparing a collagen device according to the present invention;

Figures 2A, 2B and 2C are a bottom perspective view, a side view and a top view, respectively, of a collagen device; Y

Figures 3A-3C show a collagen device made of a multilayer or laminated product.

Detailed description of the invention

It will be understood that the foregoing is only illustrative of the principles of the invention, and that several modifications can be made by those skilled in the art without departing from the scope of the invention, as defined in the appended claims.

A collagen device according to the present invention is prepared by mixing collagen with purified water for a period of time sufficient to form a mixture. The proportion of collagen with respect to purified water is between approximately 0.4% and 5.0% by weight. The pH of the mixture is then adjusted to a level of pH sufficient to substantially solubilize the collagen. A predetermined amount of the mixture is placed in a container. The mixture is then formed into a collagen sheet by means of a lyophilization process. The mixture could also be formed into a block, cylinder, or other desired shape, which will be here collectively referred to as a collagen sheet. The collagen sheet is crosslinked below. During crosslinking, the collagen sheet is preferably exposed to a liquid or vapor form of a crosslinking agent, such as formaldehyde or glutaraldehyde. Next, the collagen sheet is vented if the crosslinking agent is vapor or re-lyophilized if it is liquid. The stages of forming the mixture in a collagen sheet and crosslinking may be reversed.

The resulting collagen sheet has a plurality of pores in which a majority of the pores have a diameter of less than 10 µm, preferably, more than 80% of the pores have a diameter of less than 10 µm. More preferably, more than 90% of the pores have a diameter of less than 10 µm. Even more preferably, more than 95% of the pores have a diameter of less than 10 µm. Even more preferably, more than 98% of the pores have a diameter of less than 10 µm. And even more preferably, approximately all pores have a diameter of less than 10 µm.

Collagen sheet 100 can be cut into predetermined shapes or shaped into predetermined shapes that are sized. The sheet 100 has an upper surface 102, a lower surface 104 and a peripheral edge 106. The edge 106 of each predetermined shape may be beveled to allow a smooth profile of the edge when wetted in situ, as shown in Figures 2A - 2 C. The angle of bevel D is preferably about 30 to 75 degrees from the vertical pivoting from the upper or lower surface.

Alternatively, before crosslinking, the collagen sheet can be compressed by rollers. The collagen sheet can be compressed between about one half to one eighth of the original thickness C of the collagen sheet.

In use, for use as a dural substitute or adhesion barrier, or for short-term contact with the body for moisture retention, hemostasis, or tissue protection, the collagen sheet can be contacted with body tissue When used as an implant, the contact between the collagen sheet and body tissue is maintained. Over time, which is currently estimated at around nine (9) months, the collagen sheet is completely reabsorbed. When the collagen sheet is placed in contact with the body tissue, the collagen sheet does not stick or adhere to the instruments, including the surgeon's hands. Also, if the collagen sheet needs to be repositioned, the surgeon can do it without the collagen sheet breaking.

The collagen sheet has very good resistance properties, such as tensile strength, which makes it very easy to be handled by the doctor. In tests conducted in accordance with ASTM 638, Type V, the collagen sheet of the present invention had an average tensile strength greater than 41.4 kPa, ranging from 51.2 kPa to 67.3 kPa per batch , with an average of approximately 60.3 kPa for all batches evaluated. The collagen sheets currently available were tested and had an average tensile strength of approximately 41.4 kPa.

One skilled in the art will readily recognize that the collagen device described herein can also be used to administer biologically active agents, such as, for example, growth factors, autologous cells, bone marrow, antibiotics, anti-cancer agents, and gene and DNA constructs.

The collagen device can be used to provide a component of a multilayer or laminate product, as illustrated in Figures 3A-C. The collagen sheet 100 may include one or more layers or laminates 110, 112 as shown ( Figure 3A shows a laminate, and Figures 3B and 3C show two laminates). The described collagen sheet may be laminated or otherwise bonded to one or more of the following: film, felt, woven or nonwoven matrix, mesh or a second collagen sheet. For example, a collagen sheet as described can be combined with a waterproof film to provide a tight construction. The final multi-layer construction would be manufactured in order to improve one or more of the following characteristics: suture retention resistance, liquid impermeability, resorption duration, handling characteristics, stiffness, and / or adhesion properties to the tissues.

The collagen sheet may include a layer of a woven film or matrix at the time of processing the collagen sheet so that it is incorporated within the limits of the collagen sheet. An alternative procedure would be to apply the second layer to the collagen sheet. by various procedures, including but not limited to, adhesives, heat pressed, and combination layers during partial processing of one or both materials. The laminated or multi-layered product may include any biocompatible materials that may be resorbable, or may not be. In addition, the layer added to the collagen device may have biological active agents (e.g., antibiotics, growth factors, hemostasis factors, anticancer agents) incorporated into or on the material while it may be in the collagen device, or may not be

The various dimensions of the laminated structures may vary from dimensions coinciding with one or multiple layers having dimensions greater or smaller than one of the other layers. In this way, the preferred characteristics of a layer can be emphasized in a certain location as desired, depending on the requirements of the surgical procedure.

Example

Referring now to Figure 1, a non-limiting example of a collagen device made in accordance with the method 10 for the preparation of a collagen device according to the present invention is illustrated. The process includes a first step 12 of adding a collagen powder to purified water preferably in a proportion of about 0.4% to 5.0% by weight of collagen powder with respect to the purified water to hydrate the collagen powder. A proportion of about 0.40% to about 3.50% by weight is even more preferred. Although a ratio of about 0.60% to about 1.20% by weight is the most preferred. Collagen powder is commercially available at Datascope of 14 Phillips Parkway, Montvale, New Jersey.

The hydrated collagen is then mixed in step 14 with the purified water for a period of time sufficient to form a mixture. This period of time is preferably about three (3) to six

(6) minutes The mixture is preferably first achieved with a relatively mild mixer sufficient to solubilize the collagen with minimal or no shear of the collagen fibers. This soft mixer can be a Lightnin ™ model L1U03 mixer that mixes with a speed of 0 to 1000 rpm and is commercially available from Lightnin, which is a General Signal Coolock unit, from Dublin, Ireland.

During mixing, the pH of the mixture is adjusted to a predetermined pH level in step 16. The predetermined pH level is preferably between about 1.5 and 4.0, which is lower than the isoelectric point of the mixture. Alternatively, the predetermined pH level is preferably between about 11.0 and 13.5, which is higher than the isoelectric point of the mixture. At the beginning of the pH adjustment, a timer is started, as illustrated in step 18. The pH of the mixture is preferably achieved while the mixture is being mixed with the soft mixer at a mixing speed of between about 400 and 1000. rpm with a pH of approximately 3.0 - 3.2. To adjust the pH, 1.0 N HCl is preferably added to the mixture. Of course, although hydrochloric acid is preferably used to adjust the pH of the mixture, other acids can be used, such as, for example, acetic acid, lactic acid, or phosphoric acid.

The pH adjustment step is preferably achieved without exceeding the predetermined pH level. If the pH level is exceeded, then an additive such as NaOH would have to be added to the mixture to raise the pH level. Sodium hydroxide is preferably used to adjust the pH of the collagen solution, although other hydroxides may be used, such as, for example, other alkali metal hydroxides or ammonia hydroxides. However, the present inventors have discovered that raising and lowering or lowering and raising the pH of the mixture can cause inconsistent freezing, which may affect the desired pore size and biocompatibility due to the change in ionic strength. . Therefore, exceeding the predetermined pH level is not preferred. During the adjustment step 16, the amount of HCl added to the mixture, the pH, and a calculation of the percentage of solids concentration are determined, as illustrated in step 20.

Once the predetermined pH level is reached in step 16, the mixing is continued mixing with the mild mixer for preferably at least one (1) hour in total time elapsed from the moment the powder is added to the water. purified in step 12, as illustrated in step 22. The percentage of solids concentration is preferably within the range of 0.6% - 1.2%.

After mixing with the soft mixer, the mixture is mixed with a shear mixer, preferably at a mixing speed of between about 8000 and 9000 rpm, as illustrated in step 24. The shear mixture preferably operates at a rate that It is enough to mechanically break down the collagen powder. This shear mixer can be a Silverson ™ mixer that mixes with a speed of 0 to 10,000 rpm and is commercially available from Silverson Machines Limited of Waterside Chesham Bucks, England. The pH of the mixture is further adjusted preferably while the mixture is mixed with the shear mixer at a pH of about 3.4-3.6.

The viscosity of the mixture is measured in step 26 preferably with the start of the mixing stage 24.

The pH is raised to improve the handling properties of the sheet. This adjustment is preferably achieved without exceeding the predetermined pH level. If the pH level is exceeded, then an additive such as HCl would have to be added to the mixture to reduce the pH level.

Once step 28 has been completed, a predetermined amount of the mixture is placed in a container, as illustrated in step 30. A sufficient amount of the mixture is placed in the container so that the resulting collagen device will have thick enough to act as a dural substitute, adhesion barrier, or for short-term contact with the body for moisture retention, hemostasis, or tissue protection. The tray is preferably made of a plastic material, such as PETG. However, the trays can be made of glass, metal, ceramic, a base material coated with a non-stick surface such as TEFLON® or polished metal. The trays could also be shaped with individual compartments, each compartment being shaped with the desired final shape of the collagen device. For example, the compartments can be 2.54 cm x 2.54 cm squares, with beveled edges on each edge. Of course, many different sizes or shapes could be made with or without beveled edges, even within the same tray, to meet the surgeon's needs.

The container is placed in a chamber, as illustrated in step 32. The container can be placed on a shelf inside the chamber, and the platform has a temperature control mechanism to control the temperature of the platform, and so Both of the camera. In the present specification and below, reference will be made to the temperature of the chamber, but one skilled in the art will recognize that this includes the temperature of the shelf. The temperature control mechanism is regulated so that the temperature of the chamber is preferably greater than the crystallization temperature of the mixture. The lower surface of the container is preferably flattened so that it engages with the flattened surface of the upper surface of the platform.

The chamber temperature may be at room temperature, which is between about 15 to 25 ° C. Alternatively, the chamber may be at approximately -3 ° C. Alternatively, the chamber temperature can be adjusted well below the crystallization temperature of the mixture, at about -50 ° C to deeply freeze the mixture when placed in the chamber. If the temperature is the ambient temperature, then the chamber temperature is adjusted to a second predetermined temperature approximately slightly above the crystallization temperature of the mixture for approximately a first predetermined period of time, as illustrated in step 34. Preferably, the second predetermined temperature is from -3 ° C to -5 ° C, and the first predetermined period of time is approximately sixty

(60 minutes. The chamber is maintained at the second predetermined temperature for approximately forty-five (45) minutes.

The chamber temperature is then cooled to approximately -45 ° C for a period of approximately one (1) hour, as illustrated in step 36. The chamber is preferably maintained at this approximate temperature for at least thirty (30) minutes. .

A vacuum is then produced in the chamber, to approximately a first predetermined level sufficient to allow adequate sublimation of the ice crystals and the chamber is evacuated, as illustrated in step 38. The vacuum may occur while the temperature of the chamber is maintained at 45 ° C in step 34. The chamber can be evacuated at approximately 6.66 to 33.33 Pa. Sublimation of ice crystals results in the formation of a collagen sheet having a plurality of pores in which a majority of the pores have a diameter of less than 10 μm.

The temperature of the chamber is then raised to a sufficient temperature and maintained at this temperature for sufficient time until primary drying occurs in the mixture, as illustrated in step 40. The chamber can be heated stepwise to about -5 ° C for about five

(5) hours and this temperature is maintained for approximately five (5) hours. In this non-limiting example, the mixture is transformed by the previous steps into a collagen sheet.

As illustrated in step 42, the chamber temperature is then changed to approximately room temperature for approximately seven (7) hours. The temperature of the chamber can be raised to approximately 35 ° C for approximately three (3) hours and maintained at this temperature for a sufficient period of time, until secondary drying occurs in the collagen sheet without producing a Excessive drying or re-melting, which can be approximately seven (7) to twenty (20) hours.

Alternatively, the collagen sheet can be compressed by rollers or plates, as one skilled in the art will readily recognize. The rollers can compress the sheet between half to less than 5% of the original thickness of the sheet. The compression of the sheet can produce a collagen sheet that is more resistant than conventional sheets.

The collagen sheet is then placed in a crosslinking chamber, as illustrated in step 44. The collagen sheets can be hung in the crosslinking chamber or placed on screens. Of course, the sheets can remain in the same chamber, and cross-linking processing can take place in this chamber.

A predetermined amount of a crosslinking agent is added to the crosslinking chamber in step 46. The predetermined amount of formaldehyde is sufficient to at least partially saturate the collagen sheet. The crosslinking agent is formaldehyde, and the predetermined amount of formaldehyde can be between about 25 ml and 35 ml. (Of course, the amount of formaldehyde added depends on the number of sheets and the size of the chambers). The collagen sheet is exposed to a liquid or vapor form of the crosslinking agent. The crosslinking agent is removed from the crosslinking chamber after approximately sixteen (16) and twenty four (24) hours in steps 48 and 50.

The collagen sheet is preferably crosslinked by steam crosslinking or solution crosslinking. If a solution is used, the sheet is preferably dehydrated by lyophilization. Crosslinking agents such as formaldehyde, glutaraldehyde, carbodiimides or difunctional succinimides can be used. Alternatively, the matrix can be crosslinked by dehydrothermal crosslinking or by UV radiation.

Collagen sheets are vented between approximately eight (8) and seventy (70) hours in step 52, to remove excess crosslinking agent.

The collagen sheet is then cut into the desired shapes at a cutting station in step 54. The collagen sheet can be shaped into predetermined shapes, which are sized in size within the tray. The edge of each predetermined shape may be beveled to allow a smooth edge profile when wetted in situ. The angle of the bevel is preferably about 30 to 75 degrees from the vertical.

Each cut section of the collagen sheet is then inspected, preferably visually, in step 56. After that, some samples can be sent for testing in step 58 and the remaining cut sections can be packaged in a conventional manner. , sterilized and then sent to the end user, in step 60. The collagen sheet is tested, preferably by the ASTM E1294 test procedure, to ensure that the porosity of the sheet is less than 10 µm in step 58.

The steps of cutting the collagen sheet in the desired shapes and crosslinking can be reversed.

One skilled in the art will appreciate additional features and advantages of the invention based on the embodiments described above. Although new fundamental features of the invention have been shown, described and indicated as they apply to a preferred embodiment thereof, it will be understood that various omissions, substitutions and changes in the form and details of the devices illustrated, and in their operation, can be performed by those skilled in the art without departing from the scope of the invention, as defined in the appended claims. For example, it is expressly intended that all combinations of those elements and / or steps that perform substantially the same function, substantially in the same manner, to achieve the same results, fall within the scope of the present invention. Substitutions of elements of one embodiment described by those of another are also fully envisaged and contemplated. It should also be understood that the drawings are not necessarily to scale, but are merely of a conceptual nature. As a consequence, the invention is not limited by what has been shown and described in particular, except as indicated in the appended claims.

Claims (16)

one.

A collagen device for use as a substitute for the hard mother, the said collagen device comprising:

a crosslinked collagen sheet, said sheet having a plurality of pores, most of said pores having a diameter of less than 10 micrometers.

2.

The collagen device of claim 1, wherein the tensile strength is approximately 58.6 kPa.

3.

The collagen device of claim 1, wherein the tensile strength is greater than 58.6 kPa

Four.

The collagen device of claim 3, wherein more than 95% of the pores of the device have a diameter of less than 10 micrometers.

5.

The collagen device of any preceding claim, wherein more than 98% of the pores of the device have a diameter of less than 10 micrometers.

6.

The collagen device of any preceding claim, wherein approximately all pores of the device have a diameter of less than 10 micrometers.

7.

The collagen device of any preceding claim, wherein the collagen is a recombinant collagen.

8.

The collagen device of any preceding claim, wherein the collagen device contains an active biological agent.

9.

The collagen device of any preceding claim, further comprising, attached or incorporated into the sheet, at least one of a film, a felt, a matrix, a mesh or a second collagen sheet.

10.

The collagen device of claim 9, wherein a fluid impermeable film is attached to,

or is incorporated into the sheet.

eleven.

The collagen device of claim 9 or 10, wherein any of the film, the felt, the matrix, the mesh or the second collagen sheet contains an active biological agent.

12.

The collagen device of claim 11, wherein the first collagen sheet contains an active biological agent, and the film, felt, matrix, mesh or the second collagen sheet also contains an active biological agent, and the Active biological agent contained in the first sheet is different from the active biological agent contained in either the film, the felt, the matrix, the mesh or the second collagen sheet.

13.

The collagen device of claim 11, wherein the first collagen sheet contains an active biological agent, and the film, felt, matrix, mesh or the second collagen sheet also contains an active biological agent, and the Active biological agent contained in the first sheet is the same as the active biological agent contained in either the film, the felt, the matrix, the mesh or the second collagen sheet.

14.

The collagen device of any one of claims 8 or 11-13, wherein the active biological agent is at least one growth factor.

fifteen.

The collagen device of any one of claims 8 or 11-13, wherein the active biological agent is an antibiotic or a combination of antibiotics.

16.

The collagen device of any one of claims 8 or 11-13, wherein the active biological agent is an anticancer agent or a combination of anticancer agents.